Desulfurization of oils



Sept. 14, 1954 Frac/iana/or C. F. GERALD DESULFURIZATION OF OILS Filed March 16, 1955 M/ l/E/V TOR. Curf/s l-T Gerald Patented Sept. 14, 1954 DESULFURIZATION OF OILS Gurtis F. Gerald, Lake Zurich, Ill., assignor to Universal Oil Products Company, Des Plaines, 111., a corporation of Delaware Application March 16, 1953, Serial No. 342,469

' (Cl. nae-27) 6 Claims. i

This invention relates to a method of desulfurizing hydrocarbon fractions and in particular to a combination process comprising extraction of sulfur from hydrocarbon fractions and the subsequent hydrogenation of the extracted sulfur fraction.

It has long been recognized that combined sulfur may be removed from a hydrocarbon fraction by extracting with a suitable solvent. Suitable solvents may include hydrogen fluoride, boron trifluoride, sulfur dioxide and many others. A characteristic of solvents of this type is that they preferentially dissolve the more polar compounds contained in the fraction. When using this type of solvent an inherent difiiculty is that other polar compounds are also dissolved and removed from the hydrocarbon fraction, such as aromatic hydrocarbons and olefinic hydrocarbons. The solvent that is perhaps the most successful for removing sulfur bearing compounds with the concurrent removal of a limited number of polar compounds is hydrogen fluoride. Even when hydrogen fluoride is used as the solvent and very small amounts of polar compotuids other than sulfur bearing compounds are removed, there is a loss in yield inasmuch as the entire sulfur bearing molecule is removed from the fraction rather than the sulfur alone. This loss may be substantial since a sulfur bearing molecule in the gasoline fraction will contain, roughly, three times as much hydrocarbon as there is sulfur on a weight basis. This means that a gasoline fraction containing 1% by weight of sulfur experiences a loss of roughly 3% by weight when the sulfur is removed by extraction techniques. As the molecular weight of the fraction increases, the proportionate loss becomes greater, in that the sulfur contained in the molecule represents a lower percentage of the total Weight of the molecule. It is an object of the present invention to remove sulfur from a petroleu fraction by an extraction process and to sub uently remove the sulfur from the sulfur ng hydrocarbon molecule extracted.

It is an embodiment of the present invention to desulfurize a hydrocarbon fraction by extracting the fraction with a hydrogen fluoride-containing liquid to produce a substantially sulfurfree rafiinate phase and a sulfur-containing extract contacting the extract phase thus produced with a hydrogen-containing gas at hydrogenation conditions, separating the hydrogenate extract phase into a hydrogen sulfide-containing gas and a substantially sulfurfree liquid, and passing the sulfur-free liquid,

which contains a high percentage of hydrogen fluoride, back into extractive contact with more of the original hydrocarbon fraction.

It is a specific embodiment of the present invention to desulfurize a hydrocarbon fraction by countercurrently contacting the fraction with a hydrogen fluoride-containing liquid at a temperature of from about 50 F. to about 250 F. and sufficient pressure to maintain both the hydrocarbon fraction and the hydrogen fluoridecontaining liquid in the liquid phase, thereby producing an extract phase and a rafiinate phase, hydrogenating the extract phase, separating the hydrogenated extract phase to produce a hydrogen sulfide-containing gas and. a substantially sulfur-free liquid, and passing the latter into countercurrent contact with the hydrocarbon fraction as the hydrogen fluoride-containing liquid.

It is another specific embodiment of the pres ent invention to desulfurize a hydrocarbon fraction by countercurrently contacting the fraction with a hydrogen fluoride-containing liquid at a temperature of from about 50 F. to about 250 F. and a pressure sufiicient tomaintain both the hydrocarbon fraction and the hydrogen fluoridecontaining liquid in the liquid phase, thereby producing an extract phase and a raffinate phase, contacting the extract phase with a hydrogen-containing gas at a temperature of about 200 F. to about 600 F. and a pressure of from about p. s. i. to about 2000 p. s. 1., separating the hydrogenated extract phase into a hydrogen sulfide-containing gas and a substantially sulfur-free liquid, and passing the latter into countercurrent contact with the hydrocarbon fraction as the hydrogen fluoride-containing liquid.

One advantage of the present process is that the solvent for the extraction of sulfur bearing compounds and the catalyst for removing the sulfur from the sulfur bearing molecule and hydrogenating the fragments is the same material, hydrogen fluoride. Another advantage is that no special means is required for separating solvent from solute. The separation is automatically effected by dilution with incoming charge when the sulfur-free hydrogen fluoride-containing liquid is recycled. Another advantage of the present process is that the recycled sulfur-free hydrogen fluoride-containing liquid acts as an automatic reflux stream which prevents the carry-over of sulfur bearing compounds into the rafiinate stream.

It may be seen from the foregoing that the process of the present invention provides a means of removing combined sulfur from a hydrocarbon fraction in a manner that removes the sulfur from the hydrocarbon fraction but returns the hydrocarbon portion of the sulfur bearing molecule to the hydrocarbon fraction. By the use of the recycle type of flow of the present invention, other polar compounds that are extracted in the hydrogen fluoride treatment are also returned to the hydrocarbon fraction. The only material removed is the sulfur portion of the sulfur bearing molecule and whatever small amount of material that is cracked to normally gaseous substances. The operating conditions are preferably those that will cause cracking of a sulfur-carbon bond and hydrogenation of the two fragments without causing excessive cracking of carbon-carbon bonds. These are not impractical limitations inasmuch as much milder conditions are required to break a carbon-sulfur bond than to break a carbon-carbon bond. The process of the present invention may be applied to almost any hydrocarbon fraction but is preferably used in connection with less viscous fractions such as gas oils, kerosenes, naphthas and gasoline or any selected fractions thereof. It is preferred that the material treated by the process of the present invention is a straight run material rather than a cracked stock in that a high olefinic content may cause the formation of high polymer sludges.

The operating conditions in the extractor will be chosen to effect extraction in the most suitable manner. It is necessary that the extraction be effected in the liquid phase and therefore surficient pressure must be maintained in the extraction zone to maintain both the rafiinate and extract phases as liquids. The temperature at which the extraction is effected may range from ambient temperature to 250 F. or higher. The factors to be considered in choosing the operating temperature are, the solubility of sulfur bearing compounds in the solvent at the operating temperature, the temperature at which destructive reactions are initiated, the viscosity of the hydrocarbon fraction, the emulsion forming or foam forming characteristics in the extraction zone at various temperatures, the critical temperature of the hydrocarbon etc. It is contemplated that the most desirable operating conditions will be at a temperature of from about 100 F. to about 200 F. and at a pressure of from about atmospheric to 100 p. s. i. or more.

The operating conditions in the subsequent hydrogenation reaction zone will be chosen to selectively crack a carbon-sulfur bond but will be too mild to cause excessive destructive reactions between carbon-carbon bonds. It is desirable to hydrogenate the fragments resulting from cracking reactions and it is therefore desirable to maintain a substantial partial pressure of hydrogen in the reaction zone. The solvent, hydrogen fluoride, not only selectively dissolves sulfur bearing compounds but furthermore catalyzes cracking reactions and thereby serves a double purpose in the present process. The operating conditions chosen will largely depend upon the boiling range of the charge stock, and the amount and type of desulfurization to be effected, however, it may be stated that for the desulfurization of a gasoline or naphtha fraction that is a fraction boiling below 450 F., the reaction zone usually will be operated at a temperature of from about 300 F. to about 600 F. and at a pressure of from about 100 p. s. i. to about 2000 p. s. i. When treating a kerosene fraction the reaction zone generally will be operated at from a temperature of about 250 F. to about 600 F. and

a pressure of from about p. s. i. to about 2000 p. s. 1. When treating a gas oil or heavier fraction, the treatment usually will be effected at a temperature of from about 200 F. to about 500 F. and a pressure of from about 100 p. s. i. to about 2000 p. s. i. or more. Both the hydrogenation reaction and the cracking reaction are favored by high hydrogen pressure. The hydrogen may be from any suitable source and need not be in an extremely pure condition. It is contemplated that the hydrogen source may be from other refinery operations such as vent gas from a reforming operation or other hydrogen producing processes.

The attached diagrammatic flow drawing is presented to further illustrate the process of the present invention but is not intended to unduly limit the process to the particular embodiment shown.

Referring to the drawing, the hydrocarbon fraction to be desulfurized passes through line 1 into the lower portion of extraction zone 3, wherein the fraction is countercurrently contacted with hydrogen fluoride-containing liquid entering the upper portion of extraction zone 3 through line 2. The resultant countercurrent contact of hydrocarbon and hydrogen fluoride produces a substantially sulfur-free raffinate phase which discharges from extraction zone 3 through line 4 and a sulfur-containing hydrogen fluoride phase passing from the lower section of extraction zone 3 through line 5. Pump 6 passes the extract phase from extraction zone 3 through line 5, wherein the extract phase is commingled with hydrogen gas entering line 5 through line I. The combined stream of hydrogen gas and extract phase passes into reaction zone 8, wherein the stream is maintained at reaction conditions for suflicient time to effect the desired reactions. The efiluent stream from reaction zone 8 passes through line 9 and control valve i0 into an intermediate portion of fractionator H. In fractionator l I the effluent stream is separated into a gaseous stream which contains hydrogen, hydrogen sulfide, and other normally gaseous materials formed in the reaction, which dis charges from the upper portion of fractionator ll through line [2 and control valve l3. A liquid stream passes from the lower portion of fractionator ll through line [4 and valve 15 and at least a portion thereof is directed into the before mentioned line 2 which passes into the upper portion of extraction zone 3. Line l6 passing into line 2 is provided for adding fresh hydrogen fluoride to the system and line 11 containing valve 58 is provided for withdrawing hydrogen fluoride containing liquid from the system. Pumps and valves in the present drawing may be placed in different positions to be consistent with pressure levels maintained in various portions of the plant. Heaters, coolers, means for reflux and other necessary equipment may be added in any portion of the flow at which it is expedient to have such equipment.

Columns 3 and II will contain some means of effecting intimate contact between immiscible phases such as sieve decks, bubble cap trays, or packing which may be any standard variety including saddles, rings, pellets, etc.

Reaction zone 8 may be filled with contact material to effect improved heat transfer characteristics or turbulence in the reaction zone. The reaction zone may be provided with some means of mechanical agitation or the turbulence may be caused by diverting the hydrogen flow from line 1 directly into reaction zone 8 through high velocity jets. It is of course understood that all columns, piping, packing, etc., in contact with hydrogen fluoride will be made of ma terial that resists attack by hydrogen fluoride or solutions thereof.

I claim as my invention:

1. The method of desulfurizing a hydrocarbon fraction which comprises contacting said fraction with a hydrogen fluoride-containing liquid to produce a substantially sulfur-free rafiinate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at hydrogenating conditions, separating said hydrogenated extract phase to recover a hydrogen sulfide-containing gas and a substantially sulfurfree liquid, and returning at least a portion of the latter into contact with the hydrocarbon fraction as said hydrogen fluoride-containing liquid.

2. The method of desulfurizing a hydrocarbon fraction which comprises contacting said fraction with a hydrogen fluoride-containing liquid at a temperature of from about ambient temperature to about 250 F. and under suflicient pressure to maintain the liquid phase, thereby producing a substantially sulfur-free raffinate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at hydrogenation conditions, separating said hydrogenated extract phase to recover a hydrogen sulfidecontaining gas and a substantially sulfur-free liquid, and returning at least a portion of the latter into contact with the hydrocarbon fraction as said hydrogen fluoride-containing liquid.

3. The method of desulfurizing a hydrocarbon fraction which comprises contacting said fraction with a hydrogen fluoride-containing liquid to produce a substantially sulfur-free raflinate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at a temperature of from about 200 F. to about 600 F. and a pressure of from about 100 p. s. i. to about 2000 p. s. i., separating said hydrogenated extract phase to recover a hydrogen sulfide-containing gas and a substantially sulfur-free liquid, passing at least a portion of the latter into contact with the hydrocarbon fraction as said hydrogen fluoride-containing liquid.

4. The method of desulfurizing a hydrocarbon fraction boiling below 450 F. which comprises contacting said gasoline with liquid hydrogen fluoride at a temperature of from about 100 F. to about 250 F. to produce a substantially sulfurfree rafiinate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at a temperature of from about 300 F. to about 600 F. and a pressure of from about 100 p. s. i. to about 2000 p. s. i., separating said hydrogenated extract phase to recover a hydrogen sulfide-com taining gas and a substantially sulfur-free liquid, passing at least a portion of the latter into contact with said hydrocarbon fraction as said hydrogen fluoride-containing liquid.

5. The method of desulfurizing a kerosene fraction which comprises contacting said fraction with a hydrogen fluoride-containing liquid at a temperature of from about 100 F. to about 250 F. to produce a substantially sulfur-free raffinate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at a temperature of from about 250 F. to about 600 F. and a pressure of from about 100 p. s. i. to about 2000 p. s. i., separating said hydrogenated extract phase to recover a hydrogen sulfide-containing gas and a substantially sulfur-free liquid, passing at least a portion of the latter into contact with the kerosene fraction as said hydrogen fluoride-containing liquid.

6. The method of desulfurizing a gas oil fraction which comprises contacting said fraction with a hydrogen fluoride-containing liquid at a temperature of from about 100 F. to about 250 F. to produce a substantially sulfur-free raninate phase and a hydrogen fluoride and sulfur-containing extract phase, contacting said extract phase with a hydrogen-containing gas at a temperature of from about 200 F. to about 500 F. and a pressure of from about 100 p. s. i. to about 2000 p. s. i., separating said hydrogenated extract phase to recover a hydrogen sulfide-containing gas and a substantially sulfur-free liquid and passing at least a portion of the latter into contact with the gas oil fraction as said hydrogen fluoride-containing liquid.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,636,843 Arnold et al Apr. 28, 1953 2,655,463 Hofmann Oct. 13, 1953 

1. THE METHOD OF DESULFURIZING A HYDROCARBON FRACTION WHICH COMPRISES CONTACTING SAID FRACTION WITH A HYDROGEN FLUORIDE-CONTAINING LIQUID TO PRODUCE A SUBSTANTIALLY SULFUR-FREE RAFFINATE PHASE AND A HYDROGEN FLUORIDE AND SULFUR-CONTAINING EXTRACT PHASE, CONTACTING SAID EXTRACT PHASE WITH A HYDROGEN-CONTAINING GAS AT HYDROGENATING CONDITIONS, SEPARATING SAID-HYDROGENATED EXTRACT PHASE TO RECOVER A HYDROGEN SULFIDE-CONTAINING GAS AND A SUBSTANTIALLY SULFURFREE LIQUID, AND RETURNING AT LEAST A PORTION OF THE LATER INTO CONTACT WITH THE HYDROCARBON FRACTION AS SAID HYDROGEN FLUORID-CONTAINING LIQUID. 